Why Are My Car Tyres Cracking And What Can I Do?

Tyres are highly engineered pieces of equipment and they’re arguably one of the most important parts of your car. Without them, your car wouldn't be able to move. However, tyres don’t last forever, and there are some signs of wear and tear that you need to look out for, including cracking.

But why have your tyres cracked, and is there a way to fix them?

What causes tyres to crack?

There are a number of components that help to make tyres strong enough to hold the weight of your car and enable them to keep their shape under pressure. These components include plies (the fibres inside the tyre that give it some flexibility while maintaining its structure) and beads (steel that’s coated in rubber to create a seal between the tyre and the wheel rim).

The rubber on the outside of the tyre is made up of lots of polymers that are knitted together to form molecules. Tyre cracking is caused by these bonds breaking down. But what is it that causes these bonds to weaken in the first place?

UV rays/ extreme heat

The polymers in the tyre can expand in the heat and contract in the cold. This constant movement can weaken the bonds over time, which is when cracks begin to appear. UV rays can also have the same effect.

UV rays are one of the biggest causes of cracked tyres, because it’s nearly impossible for most people to store their tyres correctly in a garage or park in the shade all the time. However, recent technological advancements mean that you can actually paint UV-resistant paint (or sprays) in your tyres in order to protect them from UV rays.

Age

As your tyres get older, the polymers naturally weaken and begin to break down. This causes your tyres to harden and become brittle - and this loss of elasticity can mean the tyres crack. Even if your car hasn’t been driven for a few years and is stored in a garage, the tyres can still weaken and crack.

It’s actually more beneficial to drive your car every now and then instead of leaving it parked. The chemical that prevents the tyre from drying out and cracking is released when the tyre is moving. Therefore, if the car is parked for a long time, this chemical won’t be able to work efficiently.

Find out how to tell what age your tyres are here.

Water

Rubber is mainly waterproof, however water can still permeate the tyre after driving on wet roads for a prolonged period of time. This water can then have the effect of either sloshing around inside the tyre – which wears it down from the inside – or having a similar effect to potholes. As the water expands and contracts in partial cracks of your tyres, it makes them larger.

Degradation

Tyres are made of rubber, which is an organic material that’s taken from trees. This makes them biodegradable and no amount of chemicals will stop your tyres from naturally degrading over time.

Certain chemicals and compounds are applied when your tyres are made to reinforce them and slow down degradation; however, these won’t work forever.

Tyre pressure

If your tyres are inflated incorrectly, cracking can occur. With under pressurised tyres, more heat is created when you’re driving. This is because more of the surface of an underinflated tyre is in contact with the road, which creates more friction. Over pressurised tyres can add extra stress to the tyre wall and cause bulging.

You can check whether your tyres are the right pressure using a pressure meter, or through our tyre pressure checking tool. Simply input your car’s registration number and you’ll see what your recommended tyre pressure is.

Are cracked tyres dangerous?

You should avoid driving with cracked tyres. This is because the tyre’s rigidity and strength have been compromised and you could experience a blowout while driving.

If you notice cracks around your tyres, you should take your car to a garage and have new ones fitted.

Do cracked tyres need replacing?

Yes, cracked tyres should be replaced right away. It indicates that there is a problem with the tyre, which could be caused by deterioration over time, low air pressure, or a variety of environmental causes. Cracks can form on the side and top of a tyre and are a source of concern for drivers because they can render a vehicle unroadworthy, unsafe, and may lead to more problems with yourvehicle.

Are cracked tyres an MOT failure?

An MOT test will involve all four tyres being checked for damage and general wear and tear. When you take your car for its test, the tyres should have a tread depth of at least 1.6mm (the legal minimum) and there shouldn’t be any tears, bulges, or cracks around the tyre.

Your car may receive an MOT failure if it’s determined that the tyres aren’t safe to drive with. If your car does pass its MOT, it could be worth determining with the garage the state of your tyres, as they may be borderline or could need to be replaced soon. The garage will be able to tell you the tyres’ tread and what condition they’re in.

How to fix cracked tyres

It’s not recommended that you try to fix your cracked tyres as their structure has been permanently weakened and no amount of chemicals will be able to bring your tyre back. However, there are preventative measures that you can put in place when your tyres are in good condition to prevent them from cracking.

How to make tyres last longer

You should ensure that your tyres are inflated to the tyre manufacturer’s recommendations and ensure that you’re driving your vehicle regularly. Also, where possible, try to park in the shade or in a garage.

You could apply a tyre protector to your tyres regularly. There are lots of brands that create these solutions, which are made to protect the rubber from UV and environmental damage as well as repel dust, dirt, and water. Just make sure that you use a water based solution, as harsh chemicals can speed up the cracking process.

Once the tyres have begun to crack, they are still okay to drive with if the cracks aren’t too big or deep. However, the fungus that causes dry rot in wood, Serpula lacrymans, could start to attack the rubber on your tyres. By keeping your tyres clean, you’ll help to prevent the fungus from spreading further, so clean your tyres regularly with warm, soapy water.

Having a qualified professional check your car tyres can help them to last longer. Come down to your local Kwik Fit centre for a free tyre check. Or, in the meantime, if you have any questions about the condition of your tyres or tyre care in general, speak to our friendly team of experts and we can point you in the right direction.